Various optical instruments, which are designed to enable viewing of areas not easily accessible or directly available for inspection, are known in the art. In medical applications, for example, a plurality of optical instruments, such as endoscopes, arthroscopes, bronchoscopes, and the like, are used for examining the interior of body cavities ranging from ear canals to joints and lungs. Access to such cavities by these instruments is typically achieved via a natural body conduit constituting or leading to the cavity. In some cases, however, it is known to make a small surgical incision by which the instrument may gain access to the cavity.
Rigid and flexible endoscopes are known in the art. Unlike their rigid counterparts, flexible endoscopes allow access to considerably cavernous and distant areas of the body, such as the intestinal tract. However, when compared with rigid endoscopes, flexible endoscopes provide reduced image quality, are relatively expensive, and are not suitable for many applications. They are also normally not adapted to withstand sterilization by an autoclave.
Rigid endoscopes have advantages in the above respects, particularly as far as image quality is concerned. In general, a rigid endoscope comprises an elongated tube having a distal end for insertion into a body cavity, a proximal end with an eyepiece, and a plurality of lenses located inside the tube and along its length for forming an image of the body cavity, and/or objects located therein, and transferring the image to a viewing component, by which it may be viewed e.g. by a physician. Typically, the interior surface of the tube is black coated in order to prevent undesirable residual light reflections therein.
U.S. Pat. No. 5,891,015 discloses an endoscope comprising a rigid tube having a distal end, a proximal end with a viewing component including an image-sensitive surface, and an imaging system therebetween, which fully occupies the tube's interior and includes a single ashperical planar-concave front lens, a single aspherical inner lens, and two glass rods. The imaging system serves to form an image of the object and to subsequently relay it to the image-sensitive surface, which reads the image and enables it to be displayed for viewing.
U.S. Pat. No. 6,398,724 discloses an endoscope including a sealed insertion tube with a distal end and a proximal end, which is associated with a focusing assembly having optical components and being mounted in an endoscope housing to which the tube is detachably attachable. The insertion tube comprises optical elements located therein along its length and adapted to form an image of the object inside the focusing assembly, wherefrom the image is transferred by the optical components to an image plane coinciding with the image-sensitive surface of a CCD sensor. The image of the object may be focused by moving the CCD sensor so as to adjust the distance between the image-sensitive surface and the stationary image. The detachable insertion tube is autoclavable, and may therefore be sterilized alone, thereby eliminating the need to sterilize the entire endoscope, especially components thereof, such as the focusing assembly and the CCD sensor, whose adequate sterilization is considerably more complex and costly.
It is crucial for reuseable medical instruments to be sterilized before their reuse, and such sterilization is performed by various methods, such as by autoclaving. However, the delicate and complicated construction of reuseable endoscopes makes their absolute sterilization difficult to achieve.
Accordingly, a need in the art has developed for a disposable endoscope, which on the one hand, provides high quality imaging, while on the other, may be produced from relatively inexpensive components and manufactured sufficiently inexpensively as to be cost-effective for disposal after single-patient use.
Attempts to design disposable endoscopes are known and disclosures thereof include, for example, U.S. Pat. No. 4,964,710, U.S. Pat. No. 5,188,092, U.S. Pat. No. 5,892,630 and U.S. Pat. No. 5,423,312. U.S. Pat. No. 5,423,312 discloses a rigid endoscope with a disposable shaft comprising a rigid tube and a handle at a proximal end of the tube from which it may be disconnected. The rigid tube is occupied with a high refractive index rod having zero focusing power and relatively simple lenses incorporated at distal and proximal ends of the rod for image formation so as to cover a wide object field and to relay the image to a video camera. Illumination light conducting means in form of fibers, clad rods or aluminum coated transparent light conducting tube are suggested.